he's a beta, he can't get pregnant
there some spoiler
He gradually transforms into an omega each time Liu knots him; it takes a long time, it's quite a process. They spend two years apart, and after they reunite, Yeehyeon is the one who asks Liu to knot him again and complete the transformation. By the end of the novel, he is 100% an omega and becomes pregnant in the side stories.
ooh i see! so he’s not an omega yet??
No, he changes gradually. By the end of the story, he's 100% omega.
can someone spoil me if he actually got pregnant after? because i’m worried since he’s gonna drink beer which poses as a risk for fetal alcohol syndrome(⊙…⊙ )